The present invention relates generally to wheeled vehicles, in the nature of heavy duty apparatus used for construction, earth working, and earth moving and the like.
More specifically the invention relates to a braking system for such vehicles of substantial size and weight which in operation have high momentum forces created and which must be overcome in braking and stopping the vehicles.
In some vehicles of the general type to which the present invention is applied, wheeled final drive assemblies and braking systems therefore have been incorporated positionally and operationally within a vehicle wheel hub. A brake system of this type, and consisting of a disc brake system, is disclosed in U.S. Pat. No. 3,301,359, dated Jan. 31, 1967, entitled BRAKING APPARATUS, and owned by the assignor of the present application.
A braking system and mechanism disclosed in that patent, and other known systems, while proving effective in some vehicles, have disadvantages when used in vehicles of greatly increased size and weight, wherein the forces which must be overcome in braking require substantially greater braking forces.
As vehicles grow in size, larger and larger brakes are needed to cope with the increased weight factors and operational momentums involved. It has been proposed to use multiple disc brakes, and systems generally including such multiple disc brakes are known. In some known systems multiple piston actuated brakes are used. Increased brake capacity in such systems can be gained in three principal ways, namely, by increasing the diameter of the discs or brake members; by increasing the number of coacting friction surfaces; and by increasing brake application pressure. Diameter size increases are limited by manufacturing size capabilities, however. The number of coacting friction surfaces, such as discs, is limited by the efficiency of a pack, and cooling of the discs in, and the pack. Application pressures are limited by state of the art control systems for the vehicles.
In attempts to attain the required braking capacity for large machine brakes, one or more of the foregoing listed limits must be exceeded if conventional brake systems are used. Heretofore however a solution has not been reached.
Some known disc brake systems are of a normally oil flooded disc brake type, wherein the disc packs are enclosed within cavities or areas in which cooling and lubricating oils are circulated to overcome heat problems encountered when using disc brakes in heavier machines. A system, generally disclosing increased cooling capacities is shown and described in my copending patent application entitled "BRAKE LUBRICATION AND COOLING SYSTEM," Ser. No. 879,305, filed Feb. 21, 1978, now U.S. Pat. No. 4,140,198, and assigned to a common assignee herewith. Such system while constituting an improvement, does not result in fulfillment of the overall requirements of braking for the larger vehicles.